量子點紅外線偵測器之研究

Abstract

本研究主要在探討量子點中電荷對元件特性的影響。量子點中的電荷無法如同於量子井中可以自由移動，這些電荷所造成的庫侖力，對於元件特性的影響大致可分為兩部份。 第一部份探討的是量子點中的電荷如何影響QDIP的傳輸特性，光電流響應和溫度的相依性。光響應隨著溫度及偏壓的增加而上升，這是在一般量子井紅外線偵測器(QWIP)的特性中看不到的。 第二部份則是這些電荷對元件頻率響應的影響。利用在量子井紅外線偵測器所發展出來的模型，將其應用在我們的QDIP元件。我們發現QDIP的光響應大小會隨著頻率增加而減少，而同樣的情況也出現在暗電流的傳輸機制中。根據其他研究團隊所提出的解釋，我們可將光響應電流分成快速暫態和緩慢暫態兩種機制。快速傳輸是由量子井中激發出來的電子所產生。而緩慢暫態是鑿因於量子井中的電子藉由熱或光子的激發離開量子井，使得量子井帶正電，造成歐姆接面的電場增強，誘使更多的載子從歐姆接面流入量子井。我們修正QWIP的模型以符合我們QDIP的特性，雖然定量上無法找到正確的方程式，但是藉由修正的方式，可以大致解釋誤差的原因。

We study the influence of charges in QDs on the characteristic of the device. The charges in QDs can not freely move , not the same as the ones in QWs. The influence of Coulomb force caused by these charges can divide into two parts. The first part study the charges in QDs how to influence the transition characteristic, the dependence of photo response and temperature . In QWIPs, it has been confirmed that the responsivity in most devices are temperature-independent. The second part study the influence of charges on frequency response. In order to explain the phenomenon showed in QDIP, the QWIP model is utilize to explain the behavior in QDIP. From the experiment result, the photo response of QDIP is decrease as the frequency increase. It is interesting that this phenomenon also showed in dark current noise. According to the QWIP model which proposed by other groups, the current contains two component of current, which are fast transient and slow transient. The fast transient comes from the photocarriers generated from the QW. The photocarriers from the QWs induce the local positive charge and thus the slow current component which is injected from the contact to compensate the positive charge in the QWs. We modify the QWIP model to fit the characteristic of our QDIP. Although we can not determine quantitatively to find the equation, we can understand the reason of inaccuracy.